Single-engine Piston Aeroplane (SEP) — Page 58, Lesson 63

I want to walk you through the climb and cruise performance data for a Single-engine Piston Aeroplane — SEP for short. This is the start of a worked-exercise section where you learn to extract time, fuel, and distance from the climb charts, and then TAS, IAS, fuel flow, and fuel consumption from the cruise power setting tables. Let's take it step by step. We begin with two climb examples. The first one says: refer to CAP 697 Figure 2.1. The airfield is at Mean Sea Level — MSL — so the elevation is zero feet. The Outside Air Temperature, OAT, is +20°C. The mass of the aeroplane is 3650 pounds. We are climbing to Flight Level 100 — FL100 — which is 10,000 feet on the standard pressure setting, and at that level the OAT is -10°C. The question asks: what is the time, fuel, and distance covered in the climb? Then, with a 30-knot tailwind, what is the ground distance covered in the climb? The answers are given later on the page. For example 1, the time is 13 minutes, the fuel is 4.8 — I'll assume that's in US gallons or pounds, the book will clarify the unit — and the distance is 27 nautical air miles. With a 30-knot tailwind, the ground distance becomes 33 nautical ground miles — NGM. Now the second climb example. Again refer to CAP 697 Figure 2.1. The airfield is at 3000 feet elevation. OAT is +15°C. Mass is 3200 pounds. Climb to FL120 — that's 12,000 feet — and the conditions are ISA, International Standard Atmosphere. The question asks for time, fuel, and distance covered in the climb. Then it asks for the same values for the climb from 3000 feet to FL120, and the difference between the two. The answers: for the climb from 3000 feet to FL120, time is 14 minutes, fuel is 5, distance is 29 nautical miles. For the climb from 3000 feet to the starting altitude — actually, the table shows FL120 at 14, 5, 29; then 3000 feet at 3, 1, 5; and the difference is 11 minutes, 4 fuel, 24 distance. So the climb from 3000 feet to FL120 takes 14 minutes, uses 5 fuel units, and covers 29 nautical air miles. The climb from the airfield at 3000 feet to that same altitude — that's a zero climb — takes 3 minutes, 1 fuel, 5 distance? That doesn't make sense unless the 3000-foot row is the climb from sea level to 3000 feet. Let me read carefully: the table says "FL120 14 5 29", then "3000 ft 3 1 5", then "Difference 11 4 24". So the 3000-foot row is the climb from sea level to 3000 feet, and the FL120 row is the climb from sea level to FL120. The difference is the climb from 3000 feet to FL120. That matches: 14 minus 3 is 11 minutes, 5 minus 1 is 4 fuel, 29 minus 5 is 24 nautical miles. With a 40-knot headwind, the ground distance is 17 nautical ground miles. Now we move to the cruise power setting tables. Each table in the Figure 2.2 series shows performance data for a given power setting. For example, table 2.2.1 is for a manifold pressure of 25.0 inches of mercury — inHg — at 2500 rpm. The data is given for three different ISA temperature deviations: Standard Day, ISA +20°C, and ISA -20°C. Note that above a certain altitude called the full throttle height, the stated manifold pressure cannot be produced by the engine. In the shaded areas of the table, the tabulated values of manifold pressure are approximately the maximum that can be expected. To use the tables, you turn to the page for the selected power setting, then select the appropriate pressure altitude and interpolate for each single degree of ISA deviation to extract the necessary information. Interpolation between pressure altitudes is also required. Now the cruise example. Example 3 asks you to refer to CAP 697 Figures 2.2 and 2.3 and extract the following data: TAS, IAS, PPH, and USG. PPH is pounds per hour — fuel flow. USG is US gallons — fuel consumption per hour or total, the context will tell. Three conditions are given. First: 25 inches of manifold pressure at 2500 rpm, FL90 — that's 9000 feet — ISA +5°C. Second: 21 inches at 2100 rpm, FL90, ISA -15°C. Third: 23 inches at 2300 rpm, FL100, ISA +10°C. The answers are provided. For the first condition: TAS is 167 knots, IAS is 147 knots, PPH is 75.55, USG is 12.6. For the second: TAS 142, IAS 130.5, PPH 59.1, USG 9.77. For the third: TAS 157, IAS 134, PPH 65.10, USG 10.85. There is also a small table at the bottom showing ISA and ISA +20 values for what looks like a different condition: at ISA, TAS 157, IAS 156? That seems off — let me read: "ISA 157 156 137 132 66.2 64 11". That might be a different power setting or altitude. The key point is that you read TAS, IAS, fuel flow in pounds per hour, and fuel consumption in US gallons per hour from the appropriate table by matching pressure altitude and ISA deviation. So in summary: for climb, you use Figure 2.1 to get time, fuel, and distance for a given airfield elevation, OAT, mass, and target flight level. For cruise, you use the Figure 2.2 series tables for your chosen manifold pressure and rpm, then interpolate for pressure altitude and ISA deviation to get TAS, IAS, fuel flow in PPH, and fuel consumption in USG.